Novel Zn(II) heterobimetallic complexes: synthesis, characterization, density functional theory calculations, in vitro antimicrobial, anti-inflammatory and anticancer activities

Novel heterobimetallic complexes of type [Zn(L)2M2(R)4Cl2], where M = Sn(IV) and Si(IV); R = -CH3 and -C6H5, were prepared by reacting the methanolic solution of monometallic complex [Zn(L)2Cl2] with group fourteen organometallic dichloride [(CH3)2SnCl2/(C6H5)2SnCl2/(CH3)2SiCl2/(C6H5)2SiCl2]. The structures of the obtained complexes were identified by various spectrometric methods such as Fourier transformation infra-red (FT-IR), nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry, powder X-ray diffraction, molar conductivity, and UV-Vis. Density functional theory (DFT) calculations were performed to explore the quantum chemical properties of the newly designed Zn(II) complexes. In vitro antimicrobial, anti-inflammatory, and anticancer activities of Schiff base ligand [L], mononuclear complex [Zn(L)2Cl2] and its corresponding heterobimetallic complexes, [Zn(L)2M2(R)4Cl2], were evaluated. The heterobimetallic complexes exhibited higher activities against Gram-positive bacteria (Bacillus Subtilis and Bacillus cereus), Gram-negative bacteria (Xanthomonas Campestris and Pseudomonas aeruginosa), and fungal strains (Aspergillus flavus and Fusarium oxysporum) in comparison with both the Schiff base ligand and the monometallic complex. This enhanced performance of the heterobimetallic complexes can be attributed to the synergistic effect. The heterobimetallic complex [Zn(L)2Sn2(C6H5)4Cl2] showed the highest potential of inflammation inhibition with IC50 = 5.2 mu g/mL, very close to standard drug sodium diclofenac (IC50 = 4.59 mu g/mL). Furthermore, the synthesized compounds were assessed for their anticancer activity against three cell lines: human colon (HCT-116), human breast (MDA-MB-231), and human lung cancer cells (A549) using the MTT assay. The obtained results showed that the heterobimetallic complex [Zn(L)2Sn2(C6H5)4Cl2] displayed the highest cytotoxic activity (IC50 = 3.12 +/- 0.25, 3.72 +/- 0.26, and 3.94 +/- 0.14 for HCT-116, MDA-MB-231 and A549, respectively). These findings suggest that the newly formulated metal complexes could be explored further in the pursuit of drug development.